NEW YORK, April 16 (Reuters) - The gap between legal fees charged by the top-billing lawyers and those on the lower rungs is growing wider, according to a study released Monday.

From 2007 to 2011, fees charged by partners who bill at least $800 per hour increased at nearly three times the rate of those who billed less than $300 per hour, according to a joint study by TyMetrix Legal Analytics, a technology company, and Corporate Executive Board, a research firm.

The study, which analyzed billing data from about 120,000 attorneys, found that overall rates have jumped by more than 4 percent since 2009, compared with a moderate 2.3 percent boost from 2008 to 2009. From 2007 to 2008, rates jumped 8.2 percent.

Average billing rates climbed to $540 per hour in 2011 from $435 in 2007.

The rise in rates among top billers, those charging $800 or more, grew nearly five times faster than the lowest billing associates who charge about $200 per hour, the study said.

The wide disparity suggests that lawyers have wide latitude to charge steep fees for high-stakes matters but face stiffer competition when handling routine work, said Joel Henning, a consultant for in-house counsel and law firms.

Rates for attorneys working on bet-the-company litigation and big transactions are "price insensitive," said Henning, principal of Chicago-based Joel Henning & Associates.

At the same time, he said, competition has grown among lawyers who handle commodity-type work, including outsourcing firms and contract attorneys.

"The degree of segmentation in the legal market place is increasing," Henning said.

RISE INEVITABLE

The study, which used data from 4,000 law firms, found that the percentage increases in billing rates for attorneys in law firms with more than 1,000 lawyers were more than double the rates of attorneys from smaller firms. The average hourly rates from 2009 to 2011 for lawyers with 501 to 1,000 increased by 13 percent compared with a 4 percent rate increase at law firms with 1 to 50 lawyers.

The practice areas with the widest rate disparity were intellectual property and commercial contracts. The areas with the narrowest ranges were regulatory and finance.

Although clients are cutting back on the number of firms they rely on for outside legal work, the rates those firms charge has increased, the study found. Those findings run counter to the conventional wisdom, which holds that consolidating the number of outside firms will reduce a client's legal costs.

One possible reason for this finding, Henning said, is that as clients increasingly rely on one firm -- and one group within a firm -- to handle their matters, the associates on these teams become more experienced and can charge more.

The rise in billing rates overall is inevitable given the business model of law firms, said Susan Hackett, chief executive of Legal Executive Leadership, a consulting firm in Washington, D.C.

"Most lawyers are working as many hours as they can. They're unable to bill many more hours, so they raise their rates," she said.

(Reporting by Leigh Jones)

Follow us on Twitter: @ReutersLegal